Paleontology, books and other stuff.

Monthly Archives: April 2015

During the eighteenth and nineteenth centuries, Paris was a busy place for science. In 1794 the Reign of Terror ended with the establishment of a new government that was more supportive of the sciences. The old Royal Botanical Garden and the affiliated Royal Museum were reorganized as the Muséum national d’histoire naturelle. The new institution fostered many brilliant scientists, including Cuvier, Lamarck, and St. Hilaire. Among those remarkable men was Alcide Dessalines d’Orbigny, considered the founder of micropaleontology and biostratigraphy. He worked in natural history, geology, paleontology, anthropology, linguistics, taxonomy and systematics.

Alcide d’Orbigny was born in Couëron (Charente-Maritime) on September 6th, 1802. In his early youth, he developed a life interest in the study of a group of microscopic animals that he named ‘Foraminifera’ and established the basis of a new science, micropaleontology. He started at an early age working with his father, a doctor, who introduced him to the study of microscopic shells they collected from La Rochelle, a major port on the coast of France. However, Bartolomeo Beccari, was the first to study these tiny shells that could only be observed under the microscope. Beccari analysed in detail the outer and inner structure of the shell, recognising the concamerations and the coiled structure, and attributed these organisms to microscopic ‘Corni di Ammone’, continuing with the enduring confusion between ammonites and foraminifera that started in 1565 when Conrad Gesner described the nummulites collected in the surroundings of Paris. Also Giovanni Bianchi (known by the pseudonym Jaco Planco) in his work ‘De conchis minus notis’ (1739) describes numerous microforaminifera that are found in abundance on the shoreline of Rimini and assigns them the name ‘Corni di Ammone’.

Cover of De conchis minus notis and foraminifera of Rimini’s seaside figured by Bianchi (1739, Table I) and attributed by the author to microscopic specimens of ‘Cornu Ammonis’.

On November 7, 1825, d’Orbigny presented to the Académie des Sciences, the results of his observations in a work entitled ‘Tableau méthodique de la classe des Céphalopodes’. It’s clear that d’Orbigny also considered this group of microscopic shells as belonging to the Cephalopods. But he was the first to divide the Cephalopods into two zoological orders: the ‘Siphonifères‘ with intercameral siphon and ‘Foraminifères’ characterized by openings (or foramina) located in the septa separating two consecutive chambers. To illustrate his work, d’Orbigny prepared 73 plates of drawings and made models of 100 of his foraminiferal species that he sculpted in a very fine limestone.

There is a long gap between the publication of his pioneering work and his other works dedicated to foraminifera because of his long journey to South America documented in the nine volumes of his ‘Voyage dans l’Amérique Méridionale’ (1835–1847). In 1835, Félix Dujardin discovered that foraminiferans were not cephalopods, but single-celled organisms. This important discovery led d’Orbigny to exclude the foraminifera from the Cephalopods. In a work published in 1839, he traced the history of foraminiferal studies and considered them as a class for the first time, dividing the history of their study in four periods culminating with the revelation of their unicellular nature.

Operculina, showing the details of d’Orbigny’s drawings intended for the Tableau.

In the volume dedicated to the recent foraminifera collected in South America he pointed out the influence of currents, temperature and depth on their distribution patterns. In Mémoire sur les foraminifères de la craie blanche du bassin de Paris published in 1840, d’Orbigny demonstrated that foraminifera could be used for classifying geological strata.

D’Orbigny‘s legacy was extraordinary with thousands of species described, the occurrences of fossils documented chiefly in France, as well as his outstanding Le Voyage dans l’Amérique méridionale published between 1835-1847, and covering the biology, ethnology, anthropology, paleontology, and other aspects of Chile, Peru, Argentina, Uruguay, and especially Bolivia.

In 1853, Napoleon III created the Chair of Paleontology in the Muséum national d’Histoire naturelle in his honour. After his death on June 30, 1857, the collection of d’Orbigny, which includes more than 14,000 species and over 100,000 specimens not counting innumerable foraminifera stored in assorted glass bottles, was auctioned by his family. The collection was bought by the Muséum National d’Histoire Naturelle, in 1858 and registered in the catalogue of the Paleontology Laboratory of this institution.

Extinction is the ultimate fate of all species. The fossil record indicates that more than 95% of all species that ever lived are now extinct. Individuals better adapted to environments are more likely to survive and when a species does fail, it is called a background extinction. Occasionally extinction events reach a global scale, with many species of all ecological types dying out in a near geological instant. These are mass extinctions. They were originally identified in the marine fossil record and have been interpreted as a result of catastrophic events or major environmental changes that occurred too rapidly for organisms to adapt. Mass extinctions are probably due to a set of different possible causes like basaltic super-eruptions, impacts of asteroids, global climate changes, or continental drift.

George Cuvier, the great French anatomist and paleontologist, was the first to suggested that periodic “revolutions” or catastrophes had befallen the Earth and wiped out a number of species. But under the influence of Lyell’s uniformitarianism, Cuvier’s ideas were rejected as “poor science”. The modern study of mass extinction did not begin until the middle of the twentieth century. One of the most popular of that time was “Revolutions in the history of life” written by Norman Newell in 1967.

Biodiversity in the fossil record. (From Wikimedia Commons)

Over the last 3 decades, mass extinction events have become the subject of increasingly detailed and multidisciplinary investigations. In 1982, Jack Sepkoski and David M. Raup used a simple form of time series analysis at the rank of family to distinguish between background extinction levels and mass extinctions in marine faunas, and identified five major extinction events in Earth’s history: at the end of the Ordovician period, Late Devonian, End Permian, End Triassic and the End Cretaceous. These five events are know as the Big Five. The most recently identified mass extinction occurred during the Middle Permian, about 262 million years ago, and it was first recognised in the marine realm as a turnover among foraminifera, with fusulinaceans among the principal casualties. The crisis also affected numerous other shallow-marine taxa, including corals, bryozoans, brachiopods, bivalves and ammonoids. Until now, all detailed studies have focused on equatorial sections, especially those of South China. That extinction coincide with the Emeishan large igneous province. But, new data indicates that at the same time there was two severe extinctions amongst brachiopods in northern boreal latitudes in the Kapp Starostin Formation of Spitsbergen, an island roughly 890 km north of the Norwegian mainland.

Fusulinids from the Topeka Limestone (Upper Carboniferous of Kansas, USA) From Wikimedia Commons

The Kapp Starostin Formation contains cool-water boreal faunas that include abundant siliceous sponges, brachiopods, and bryozoans. The widespread and near-total loss of carbonates across the Boreal Realm also suggests a role for acidification in the crisis. This extinction predates the end-Permian mass extinction, because a subsequent recovery of brachiopods and especially bivalves is seen in the Late Permian. This post-extinction fauna disappears 10 m below the top of the Kapp Starostin Formation and thus fails to survive until the end of the Permian (Bond et al., 2015). This is a true mass extinction because the new data suggest that about 50 per cent of all marine species died during the event.

Oceanic oxygen depletion represents a potent cause of extinction in marine settings, and is often linked with volcanic activity, warming, and transgression. However, the role of anoxia in the wider Capitanian extinction scenario remains enigmatic. Volcanically induced effects are multiple and include acidification.

Acidification affects the biogeochemical dynamics of calcium carbonate, organic carbon, nitrogen, and phosphorus in the ocean and interferes with a range of processes, including growth, calcification, development, reproduction and behaviour in a wide range of marine organisms like foraminifera, planktonic coccolithophores, pteropods and other molluscs, echinoderms, corals, and coralline algae. Ocean acidification in the geological record, is often inferred from a decrease in the accumulation and preservation of CaCO3 in marine sediments, potentially indicated by an increased degree of fragmentation of foraminiferal shells. But, recently, a variety of trace-element and isotopic tools have become available to infer past seawater carbonate chemistry.

Undoubtedly, the proximity of the End Permian extinction, makes difficult to determine if these events are separate or are part of a the same event.

Bold capital letters spell out the above chilling sentence on the back cover to Michael Crichton’s sequel to Jurassic Park. No blurb. No description of the novel. Those three words say enough.

That short, simple, yet powerful sentence could be used for one of the most famous events in geological history: the K-T extinction. This is now formally known as the K-Pg extinction and heralds the end of the Cretaceous Period and the beginning of the Paleogene Period. It still marks the same asteroid impact that happened 66 million years ago and the end of the non-avian dinosaurs. But something has survived. The avian dinosaurs we see every single day: birds.

In Paleogene park: something has survived.

This may seem a little over the top. But we are not talking about blue tits, or blackbirds. There were once bigger avian dinosaurs running extremely…

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Permian SeafloorPhotograph by University of Michigan Exhibit Museum of Natural History.

About one third of the carbon dioxide released by anthropogenic activity is absorbed by the oceans. But the CO2 uptake lowers the pH and alters the chemical balance of the oceans. This phenomenon is called ocean acidification, and is occurring at a rate faster than at any time in the last 300 million years (Gillings, 2014; Hönisch et al. 2012). Acidification affects the biogeochemical dynamics of calcium carbonate, organic carbon, nitrogen, and phosphorus in the ocean and interferes with a range of processes, including growth, calcification, development, reproduction and behaviour in a wide range of marine organisms like planktonic coccolithophores, foraminifera, pteropods and other molluscs, echinoderms, corals, and coralline algae. Rapid additions of carbon dioxide during extreme events in Earth history, including the end-Permian mass extinction (252 million years ago) and the Paleocene-Eocene Thermal Maximum (PETM, 56 million years ago) may have driven surface waters to undersaturation.

The end-Permian extinction is the most severe biotic crisis in the fossil record, with as much as 95% of the marine animal species and a similarly high proportion of terrestrial plants and animals going extinct . This great crisis occurred about 252 million years ago (Ma) during an episode of global warming. The cause or causes of the Permian extinction remain a mystery but new data indicates that the extinction had a duration of 60,000 years and may be linked to massive volcanic eruptions from the Siberian Traps. The same study found evidence that 10,000 years before the die-off, the ocean experienced a pulse of light carbon that most likely led to a spike of carbon dioxide in the atmosphere. Volcanism and coal burning also contribute gases to the atmosphere, such as Cl, F, and CH3Cl from coal combustion, that suppress ozone formation.

Image that shows field work in the United Arab Emirates. Credit: D. Astratti

Ocean acidification in the geological record, is often inferred from a decrease in the accumulation and preservation of CaCO3 in marine sediments, potentially indicated by an increased degree of fragmentation of foraminiferal shells. But, recently, a variety of trace-element and isotopic tools have become available to infer past seawater carbonate chemistry. The boron isotope composition of carbonate samples obtained from a shallow-marine platform section at Wadi Bih on the Musandam Peninsula, United Arab Emirates, allowed to reconstruct seawater pH values and atmospheric pCO2 concentrations and obtain for the very first time, direct evidence of ocean acidification in the Permo-Triassic boundary. The evidence indicates that the first phase of extinction was coincident with a slow injection of carbon into the atmosphere, and ocean pH remained stable. During the second extinction pulse, however, a rapid and large injection of carbon caused an abrupt acidification event that drove the preferential loss of heavily calcified marine biota (Clarkson et al, 2015).

The increasing evidence that the end-Permian mass extinction was precipitated by rapid release of CO2 into Earth’s atmosphere is a valuable reminder for an immediate action on global carbon emission reductions.